What do you mean by wireless dashcam? Do you mean WiF? Front/rear channels wireless?
As to installation, it depends on the camera, your car, single or dual channel (or more), hardwired, battery pack etc. I would say easily $200 on a basic setup.
Most handy guys/gals can install it, actually not too difficult. Just need some trimming tools (cheap online). If you want to hardwire to car fuse or hardwire a battery pack, you will need additional tools like a crimper, fuse taps, a circuit tester or multimeter.